The present invention relates to a method for preparing a foam composition from cellulosic products such as papermill sludge, waste paper scraps, wood chips, sawdust, wood particles, and the like.
In the manufacture of paper, a variety of materials are added to the paper pulp prior to and during the sheet-forming operation for the purpose of producing desired properties in the finished paper, such as proper surface, opacity, strength, and feel. For example, finely ground inorganic fillers such as talc, certain clays, calcium carbonate, blanc fixe, and titanium dioxide, are added to all papers, except absorbent types (tissue or blotting paper), to improve surface smoothness, whiteness, printability, and opacity. Sizing agents, such as soaps, gelatins and rosins (with alum), wax emulsions and starches, are added to most papers for improving resistance to penetration by liquids. In addition, coloring agents, such as acid, basic, direct, and sulfur dyes and natural and synthetic pigments are added to most pigments.
Substantial quantities of water are recovered during the sheet forming operation and recycled to the process after filtering. The solid residue or so-called papermill sludge separated from the recovered water primarily contains wood fibers and additive materials, particularly filler such as clay. Uses for this sludge are quite limited and, consequently, it is often disposed of as waste. Thus, some effort has been made to develop new uses for this waste product.
Another waste product for which disposal is a problem is paper, such as office waste paper, cellulose packing waste such as cardboard packing boxes, and the like. Office waste paper cannot be used in conventional cellulose blown-in insulation because most paper used in offices has been treated with clay fillers. The borate flame-retardants used with conventional cellulose insulation do not adhere well to paper particles which have been treated with clay. Packaging materials such as cardboard boxes likewise are not suitable for use in conventional cellulose insulation, as the glues used in making these boxes provide food for rodents and insects.
Yet another cellulosic product for which uses must be found is wood waste products, such as wood chips, sawdust, wood particles, and the like. These cellulosic materials are sometimes used in making particle boards which are often replacements for wood as building materials.
Haataja et al, in U.S. Pat. No. 4,221,751, disclose a process for making pallets from papermill sludge by blending dried, comminuted papermill sludge with a fibrous reinforcing material and a resinous particle board binder. Suitable binders for use in this process include thermosetting resins such as phenolformaldehyde, resorcinolformaldehyde, melamine formaldehyde, urea formaldehyde, urea furfural, and condensed furfuryl alcohol resins, and organic polyisocyanates, either alone or combined with urea- or melamine-formaldehyde resins.